1. Field of the Invention
This invention relates to an apparatus and method for the removal of flashing from elastomeric elements after they have been molded. More particularly, it is directed to a refrigerating and tumbling device for achieving deflashing of such elements.
2. Description of the Prior Art
The manufacture of molded elements from elastomeric materials, such as, synthetic and organic rubbers, as well as silicone rubbers, is well known. In the manufacture of such materials, a thin extraneous membrane (called "flashing") of the elastomer forms about the edges of the main body of the molded part. In the finishing of the molded part, it is necessary that the flashing be removed.
In the past, flashing was removed by manual methods which, of course, proved to be extremely slow and economically unfeasible. Cryogenic deflashing methods have been developed which utilize the principle that the very thin flashing membranes freeze much more quickly than the body of the molded element, when frozen, the flashing becomes extremely brittle, and when impacted with other molded parts or appropriate media, e.g., sand or other particulate material, the frozen, brittle flashing membrane breaks cleanly at the edge of the molded element. This results in a smooth surface, free from the undesirable flashing membrane.
The devices and methods used heretofore for cryogenic deflashing of such elements have relied on quick freezing of the elements using extremely cold temperatures, i.e., temperatures in the range from -32.degree. C. to -150.degree. F. For this purpose, the art has used solid or liquefied carbon dioxide or liquid nitrogen. Typically, the molded parts to be deflashed are immersed in the solid or liquid carbon dioxide or liquid nitrogen in a vessel which contains, if desired, an appropriate deflashing media. The vessel is rotated or vibrated so as to cause impact between the parts and/or media. The flashing membrane freezes to brittleness and easily breaks away upon impact.
Because of the nature of the cryogenic materials, e.g., liquid nitrogen, liquid carbon dioxide, and solid carbon dioxide, the devices for use with such materials are necessarily relatively complicated and expensive. Because such materials are or become gaseous, they generally result in pressure build-ups so that the apparatuses must be sufficiently structurally strong to withstand the higher pressures resulting from these materials. In addition, substantial insulating must be used with the devices because of the "quick freeze" aspect of the cryogenic materials.
Because of the extremely low temperatures accompanying their use as well as the pressure build-up, there is also a safety problem and the devices must be equipped with appropriate safety mechanisms to avoid accidents. Also, of course, appropriate storage tanks must be provided with such devices to provide for holding the cryogenic materials during their use.
All of this contributes to the increased complexity and costs of these prior art devices. In addition, the use of the cryogenic materials, in and of itself, provides a storage and handling problem for the user. Normally, smaller elastomer finishing operations do not have or cannot afford to maintain the expensive facilities needed to store significant amounts of the cryogenic materials on site. As a result, the cryogenic materials must be delivered shortly before their use. This can cause supply problems if the cryogenic materials cannot be provided at the time necessary for their use in the deflashing apparatus. Of course, the cryogenic materials themselves are relatively expensive.
An additional problem with the prior devices is that their use is accompanied by an extremely high noise level, particularly, when a number of the machines are being used at the same time. Usually, workers in the area are required to wear ear protection because of the intensity of the noise. In addition, these machines generate a substantial amount of dust. Each of these disadvantages results in the machines normally being kept in a separate room in order to isolate both the noise and the dust from other areas of the workplace.
Also, because of the relative complexity of the machines and the necessity for having a source of liquid nitrogen close at hand, as well as the pressures which are generated in the devices, the machines are normally fixed in place. Thus, they are not easily movable from one area to another.